The invention relates to a touch sensor to be used for controlling a dimension or a position of a workpiece.
Conventionally, as a touch probe in a three dimensional measuring system, a structure as disclosed in U.S. Pat. No. 4,339,714 has been well known.
More specifically, in U.S. Pat. No. 4,339,714, as shown in FIGS. 9-11, a probe 12' is provided with a contact 15' having a spherical end 16', which contacts an object 11' to be measured. The contact 15' has the other end provided with three arms 18' arranged radially and housed in a case 14' of the probe 12'. The three arms 18' arranged radially are provided with a pair of electrodes 17', respectively.
The electrodes 17' and a coil 20' are connected in series through a monitoring circuit 19', and a capacitor 22' is arranged parallel to the coil 20'. When a measuring is carried out, the probe 12' is moved so that the contact 15' touches the object 11' to be measured. When the contacts 15' touches the object 11', the contact 15' in a rest state is moved to thereby separate from at least a pair of electrodes 17'. Thus, the circuit 19' is opened. By opening the circuit 19', it is realized that the probe 12' contacts the object to be measured.
In the above structure, in case a position of a tip of a cutting blade, such as a bit of a lathe, is regulated, it is required to measure a position of the tip of the cutting blade along a rotational center line, i.e. X--X' direction of the object to be cut, e.g. positioning a bit for cutting a right side and a bit for cutting a left side, and to measure a position of the tip of the cutting blade in a direction of Y--Y' perpendicular to the X--X' direction, e.g. positioning a flat bit and a drilling bit. In this case, it is impossible to output positional data relative to which direction the data are among the four X, X', Y, Y' directions, as well as a positional information.
As a conventional example wherein a directional information as well as a positional information can be outputted, a plan view of the example is shown in FIG. 7 and a front view thereof is shown in FIG. 8.
More specifically, individual touch sensors 21, 22, 23, 24 are provided on a main body 25 in the four directions of X, X', Y, Y', respectively. Reference numeral 26 represents a flange for fixing the main body 25 to, for example, an end of an arm fixed to a fixing portion on a main shaft side of a lathe.
In the above structure, surfaces to be touched are separated by several tens of millimeters, so that when the sensor is to be fixed to a lathe or the like, there is no space for fixing the sensor. Also, in case two bits are arranged parallel with a narrower space therebetween, which is less than a space between the surfaces to be attached, it is impossible to measure by the sensor. Further, since four touch sensors are provided in respective four directions, a production cost thereof is increased.
Therefore, an object of the present invention is to provide a touch sensor capable of outputting positional data relative to which direction the data relate among the four directions of X, X', Y, Y', as well as a positional information.
Another object of the present invention is to provide a touch sensor as stated above, wherein a distance between surfaces of the sensor to which a bit or the like touches is extremely shortened, so that the sensor is very compact and handy.
A further object of the present invention is to provide a touch sensor as stated above, wherein the sensor can be easily manufactured at a low cost.
Further objects and advantages of the invention will be apparent from the following description of the invention.